The present invention relates generally to a piezoelectric actuated fuel injector for use in conjunction with an internal combustion engine and, more particularly, to a method for detecting injection events in a piezoelectric actuated fuel injector.
Fuel injectors for high pressure injection of fuel directly into the combustion chamber of the engine generally use a guided needle-type injector valve which seals against the valve seat, thereby closing the fuel discharge openings. In the open position, the injector valve axially separates from the valve seat, thereby allowing fuel flow out of the discharge openings into the combustion chamber. In order to minimize emissions and improve combustion efficiencies, engine manufactures are adamant in their desire to establish control over the timing and rate at which fuel is injected through the discharge openings and into the combustion chamber of the engine.
Conventional fuel injectors use a magnetic solenoid to actuate the injector valve. However, solenoid actuated fuel injectors introduce a significant delay between the drive voltage application and event performance which in turn may prevent meaningful control over the rate of injection.
Alternatively, fuel injectors may use piezoelectric actuator to actuate the injector valve. In one instance, the injector valve is quasi-directly actuated by a piezoelectric actuator. In the another instance, the injector valve is actuated through the use of fluid pressure acting on the valve. A control chamber is used to store the fluid that acts on the injector valve, whereby changes in the fluid pressure actuate the injector valve. A control valve that controls the fluid pressure in the chamber is actuated by a piezoelectric actuator. In order to establish meaningful control over the timing and rate of injection, it is desirable to provide a method for detecting injection events in a piezoelectric actuated fuel injector.
In accordance with the present invention, a method is provided for detecting injection events in a piezoelectric actuated fuel injector. The method comprises the steps of: (a) providing a piezoelectric element for actuating the injector valve; (b) controlling a voltage applied to the piezoelectric element, thereby actuating the injector valve; and (c) monitoring at least one of the voltage or current associated with the piezoelectric element, wherein changes in voltage or current are indicative of injection events in the fuel injector.
For a more complete understanding of the invention, its objects and advantages, refer to the following specification and to the accompanying drawings.